1. Field of the Invention
This invention relates to a motion and trajectory data generator for a platform having multiple degrees of rotational freedom, and more specifically pertains to a motion and trajectory data generator for a multi-gimbaled rotating platform supporting a projectile having an inertial navigation system.
2. Description of Related Art
There have been recent developments directed toward equipping projectiles with an inertial navigation system. In these applications, the inertial navigation system (INS) is incorporated into the projectile in order to guide the projectile to a desired target location. It is common for such guided projectiles to be launched from a launcher platform having several degrees of rotational freedom in order to position the projectile to a desired launch position.
In order to evaluate the performance of a guided projectile without having to field test the guided projectile through an actual launch, simulated launches are often performed using pertinent data related to the launches. Information obtained from a simulated launch can be utilized to align and calibrate the INS of the guided projectile. Furthermore, the movement of the launcher platform can be used to align and calibrate the INS in the guided projectile with respect to Earth. Unfortunately, existing motion and trajectory simulators are only designed to simulate the trajectory of the guided projectile through its flight path, where such existing motion and trajectory simulators do not deal with the types of motion encountered on a typical launcher platform. For instance, when a launch is initiated for the projectile, the launch platform must reposition from its current location to its desired launch position. There is currently no way of simulating the motion of the launch platform or the effect of its motion on the launch without actually moving the launch platform in a field test.
Furthermore, in current simulators, rotation rates are generated by coordinated turns which do not address the situations of multi-gimbaled coupled rotations, as experienced by most launch platforms. Generating realistic motions such as those experienced by a multi-gimbaled launch platform is not possible using conventional simulators as rotations must be generated about constrained degrees of freedom. Additionally, the starting and stopping characteristics of the motion of the launch platform must be taken into account in order to simulate realistic inertial data which would be sensed by an INS in the projectile carried on the launch platform. Conventional simulators fail to account for these starting and stopping inertial characteristics.
Thus, there is clearly a need for a motion and trajectory data generator for providing simulated data for the movement of a launch platform carrying a projectile to be launched to permit evaluation of the projectile launch without actual field testing. Moreover, there is a need for a motion and trajectory data generator for providing simulated data for a multi-gimbaled rotating launch platform.
The present invention provides a system and method for generating motion and trajectory data for a multi-gimbaled rotating platform. A motion generating unit is provided for generating a set of motion equations for each degree of rotational freedom of the multi-gimbaled rotating platform, where the set of motion equations define the rotational movement of the platform about the pivot point of the gimbals between their starting position and ending position. Movement characteristics of the gimbals are provided to the motion generating unit for computing the set of motion equations, where the movement characteristics include a maximum angular acceleration, a maximum angular deceleration, a maximum angular rate, and a step angular jerk of the gimbal. Furthermore, the starting and ending positions of the gimbal are also provided to the motion generating unit. From these values, the motion generating unit generates a set of motion equations which define the movement of the gimbal between its starting position and its ending position during rotation of the platform. The set of motion equations define an angular acceleration, an angular rate, an angular displacement, and an angular jerk for each gimbal.
Once the set of motion equations for each gimbal of the multi-gimbal rotating platform are generated, it is possible to utilize these gimbal motion equations to compute trajectory data for an object being supported by the platform. The present invention utilizes the set of motion equations simulating movement of the rotating platform to generate trajectory data for the object with respect to Earth, so that the effect of the motion of the rotating platform on the object can be simulated without requiring the rotating platform to be actually moved in a field test. An attitude/position processing unit generates a second set of motion equations which define the movement of the object being supported by the rotating platform, wherein said second set of motion equations include a relative acceleration, velocity, and position experienced by the object on the platform as well as attitude information and a relative body rate of the object.